Valve for steam-engines.



PATENTED DEC. 1, 1903.

DE WITT 0. PRESCOTT. VALVE FOR STEAM ENGINES.

, APPLICATION FILED JUNE 12, 1903.

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UNITED STATES Patented December 1, 1903.

PATENT OFFICE.

DE WITT C. PRESCOTT, OF CHICAGO, ILLINOIS, ASSIGNOR OF THREE- FOURTHS TO LOREN' L. PRESCOTT, EDWARD L. PRESCOTT, AND SUMNER K. PRESCOTT, OF MARINETTE, WISCONSIN.

VALVE FOR STEAM-ENGINES.

SPECIFICATION forming part of Letters Patent No. 745,520, dated. December 1, 1903. Application filed June 12, 1903. Serial No, 161,143. (No model.)

To all whom it may concern;-

Be it known that 1, DE WIT'r C. PRESCOTT, a citizen of the United States, and a resident of Chicago, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Valves for Steam-Engines, of which the following is a specification, and which are illustrated in the accompanying drawings, forming a part thereof.

This invention relates to that type of reciprocating steam-engine in which the piston moves between positive stops and in which thereis no automatic reversing-valve.

The object of the invention is to provide for the retardation of the engine by restricting its exhaust while allowing a full head of steam for driving it, and particularly to provide adjustable means for varying the restriction of the exhaust to adapt the engine to the load.

The invention consists in a piston-valve having a lap at each end of sufficient length to always cover the exhaust-port, such lap being provided with a series of apertures, so

that there may be a graduated opening of the exhaust-port of the cylinder; and it consists, further, in a novel adjustable stop mechanism for variably limiting the throw of the valve. In the accompanying drawings, Figure 1 is a side elevation of the engine, the v'alve-cas ing being-shown in longitudinal vertical central section. Fig. 2 is an end elevation of the engine. and Fig. 4 is a detail of the valve-casing.

There is shown at 10 a base for the engine, such as to adapt it for mounting upon a sawmill-carriage; at 11, the engine-cylinder; at 12, its piston-rod; at 13, its cross-head; at 14, a rocker-shaft; at 15,- a crank-arm fixed to the rocker-shaft; at 16, a link connecting the cross-head with the crank-arm; at 17, the valve-casing; at 18, the cylinder-valve; at 19, the valve-stem; at 20, the valve-lever, and at 21 the bracket upon which the valve-lever is pivoted and which rises from the base 10. Steam enters the valve-casingthrough the pipe 22, and the exhaust is led therefrom through the pipe 23. The induction pipe communicates with the steam-port 24, which Fig. 3 is a detailof the valve,,

I is at the middle of the valve-casing, and the exhaust-pipe communicates with the ends of the valve-casing through the passages 43 i4. The valve 18 is provided with a central chamber having ports 27 28 at each end thereof, which are adapted to register alternately with the cylinder-ports 29 30. The end laps of the valve are prolonged, so that they never fully uncover the cylinder-ports to the exhaust-ports of the valve-casing. These laps are apertured, as shown at 31 32, the former series of apertures coming first into registry with the cylinder-ports and not being of sufficient area in the aggregate to fully open the same, so that they provide but a restricted exhaust, the latter series of apertures also coming into registry with the cylinder-ports when the valve is still further moved, so that a more free exhaust is permitted. The steamports 27 28 of the valve are sufficiently large, so that as soon as they come into registry with the cylinder-ports a full head of steam is provided.

The valve-lever moves between positive stops 33 34,which are shown as flanges formed on the bracket 21, to which the lever is pivoted, and adjustable stops are provided in the form of bolts 35 36, which set through these flanges, each bolt being provided with a j am-nut 37 for locking it in its adjusted positiou'.

o A slide-block 38 is mounted upon the valvelever and is tapering or wedge-shaped and serves as the abutment for contacting with the stop-bolts 35 36. The block 38 is moved by means of a bell-crank 39, pivoted to the v valve-lever, one arm of this bell-crank constituting a handpiece and the other arm therewidely, while if 4 the load be light he lowers the block, and thus provides for a restricted opening of the exhaust-ports.

Preferably an adjustable stop is provided to limit the downward movement of the block 38, so that there may under all circumstances be some movement of the valve. Such a stop is shown in the form of a threaded rod, pivotally attached to the upper end of the valve-lever and projecting through a suitable aperture in the hand member of the bell-crank 39 and carrying at its outer end a milled nut.

I claim as my invention 1. In a steam-engine, in combination, a cylinder having ports leading to each of its ends, a valve-chest with which such ports communicate and having induction and exhaust ports, a valve having graduated exhaust-controlling ports, a valve-controlling lever, positive stops limiting the range of the lever throw, and a slide-block carried by the lever and having inclined faces cooperating with the stops.

2. In a steam-engine, in combination, a cyl- 3. In a steam-engine, in combination, a cylinder having ports leading to each of its ends, a valve-chest with which such ports communicate and having induction and exhaust ports, a valve having graduated exhaust-controlling ports, a valve-controlling lever, adjustable positive stops limiting the range of the lever throw, and a slide-block carried by the lever and having inclined faces cooperating with the stops.

DE WITT (J. PRESCOTT.

Witnesses:

Louis K. GILLsoN, E. M. KLATCHER. 

